International Conference on Physics of Solar Energy, 1976
Qaryounis University, Libya (now known as University of Benghazi)
vintage promotional ruler was created as a commemorative item for an international solar energy academic conference hosted by the university's physics department in April 1976
unit of measurement is centimeters (cm), with each numbered major line representing one centimeter (from 16 to 23).The smaller subdivision ticks between each number represent millimeters (mm).
see pics for scale